Cellulose acetate molding compositions



' perature, so that it can be molded satisfactorily acetate which haveunique characteristics of 15 25 tionable not only because of the cost ofapplying These O j ts e acwmplished; in da c 25 A unheated injectiondie.

Patented ar.,1 ,1 '93s i 2,109,593

UNITED STATES PATENT OFFICE (2,109,593 I CELLULOSE'ACETATE MOLDINGCOMPOSITIONS Mauricev L. Macht,- Jersey CityQand David A. Fletcher,Arlington, N. J., assignors to E. I.

du Pont de Nemours'& Company, Wilmington, DeL, a corporation of DelawareNo Drawing. Application October 28, 1936, Serial No. 108,098 l a 10 clims. (01. 106-40) This invention relates to the preparation of increaseof plasticizer content, in order to make molding compounds of celluloseacetate, and the molding more easy, will have the result ormoreparticularly to the formulation'of such dinarily of improving thetoughness, both incompounds having unique'p'roperties. herontly andbecause a readily molded composi- It is ordinarily required thatarticles molded tion becomes more thoroughly welded in the 5 fromcompounds of a base of cellulose acetate molding; but the increase ofplasticizer content possess a considerable degree of rigidity as welldiminishes the rigidity of the mass and also has as of toughness, thatthe material be of high the result of'depressing the softeningtemperasoftening temperature and of low burning rate, ture of the moldedarticle, thus limiting the 10 and that the molded article be free fromexud'autility of the article and necessitating the appli- 10 tion.. Atthe same time it is required, particucation of more drastic cooling inorder to harden larly when the molding is done by the method of thearticle sufficiently for removal from the mold.

injection, that the compound have a satisfactory It is an object of thepresent invention to fordegree of mobility at a reasonable moldingtemmulate molding compounds of a base of cellulose r a d rapidly, easymolding,-whether- .by the compression orby compression molding, if thmolding comthe injection method, and which at the-same time pound doesnot flow readily when heated, it will' yield articles of a de of d yd adegree require either the application of excessive t of toughness notheretofore associated with such perature, or of molding temperature foran exmolding characteristics, and which furthermore 20 cessive time,either of which is almost certain to e free from exudati n un r xtrem od cause discoloration-and even 'may cause decom- A further Object iS DPe eXlldaposition and bubbling of th ma o else th tion. of' certainplasticizers. Other objects will use of abnormally high pressure, whichis objecpp ereinafter.

suc'h pressure-in that the equipment must be With the present invention,by compo made correspondingly massive and rugged, but D ,-De 100 par sof Cellulose acetate, from also because dies may be definitely andperma- I 20 to 60 parts of certain mixtures of plasticizers, ,nentldamaged by being subjected to molding of whic x r m 8 to 3 p r en iscampressures above -the ordinary range. D1 a d t e ba ce e t e (A) o e 0m ie 30 In injection molding it is even more important plasticizers 0ftoughening exuding yp that a high degree of mobility be developedwithfrom 31 t 69 P nt Of toughening exuding out the use of excessivetemperature, both bep a r together i fr m 23 to 31 P c cause theduration of the heating is ordinarily offire-retarding plastic ze (C)from 25 to 35 longer than in compression molding and because 67 P c Otoughening x di plas eizer to 35 the process is dependent, foreconomical operagether mm from 2 t 31 Percent Of fi eetardtion,.upon theease of. flow'of the heated matee p ast o r a d m 2 t 6 p t o an a ylrial through a restricted orifice. It -is particus p id pla e th sa dtou henin larly desirable that an injection molding comexuding, fire e ad d y Sulphonamide 40 pound have a high rate of softening with increaseplasticizers being selected from respective groups 40 of temperature,or, otherwise stated, that the inhereinafter enumerated. I I tervalbetween'molding temperature and SOfte The invention rests upon thediscovery of the i temperature e p t v y small, othat unexpected results.-of -'certain combinations -of the molded mass W111 quickly becomerigid 1n the known plasticizers'.

The' requirements 'of mobility, toughness and Therelis rcogmzedth-e-artu.mrepr f 'rigidity are characteristically contradictory, soveil-defined classiof plas.tmlzers' mcmdmgthat it has been difiicult orimpossible to meet i f ch-emmny dwerFe i f them all'in a singlecomposition. Thus rigidity F mm by i e mmmct-lon 0 is orainarilypredicated upon relatively low p1as with cellulose acetate, compositionsof distinct 5O ticizer content, and this in turn makes the mate-'toughness' but 'Charagterized having Some- -rial less readily moldable,so that unless the contendency to exude from h finished-111616166-ditions of molding are extreme, it is likely to be time, when used inconjunction with Cellulose inadequately welded by the molding process,and acetates in the lower a es of acetic number, hence deficientinstrength and toughness. ,An- Such as those of between about 48 and 53which 5-5 are the most frequently used in the manufacture of plastics.Some of them, when used with cellulose acetates of higher aceticnumbers, such as those of between about-53 and 54.5 are comparativelyunobiectionable in this respect. Exudation, however, is frequentlyaggravated by the presence, in the composition, of'mold lubricants, theuse of which is very generally desirable. To prevent exudation it hasfrequently been necessary to restrict rather severely the proportion ofsuch a plasticizer used.

Among these toughening exuding plasticizers may be named diethylphthalate, dimethoxy ethyl phthalate, triethyl citrate, diethyleneglycol di-isobutyrate, diethylene glycol dipropionate, dimethylhexahydro phthalate, diethyl adipate, methyl phthalyl ethyl glycollateand ethyl phthalyl ethyl glycollate.

Triplienyl phosphate is the most important member of an establishedclass of fire-retarding plasticizers. It has been fully recognized,however, that the proportion of it which may be used is distinctlylimited because of its comparatively weak plasticizing action and poorcompatibility with cellulose acetate, which resultin brittleness andexudation. In general, it has been used solely to take advantage of itsfire-retarding property where this overbalances itsinherent'disadvantages in other respects. Other plasticizers used forthe same purpose and subjectto similar limitations are tricresylphosphate and trithio phenyl phosphate. retarding character, and alsoshares the general properties of the toughening exuding plasticizers.

The aryl sulphonamide plasticizers have come to be recognized by lack ofstrong solvent power toward cellulose acetate except with the assistanceof heat or a suitably selected proportion of solvent, and by a ratherstrong tendency to exude from such compound when used without otherplasticizers, or even with certain other plasticizers. The arylsulphonamide plasticizers have and para toluol ethyl sulphonamidestogetherwith the closely related compound para toluol sulphonanilide.

Other individuals of related character, which approach more or lessclosely in behavior to those enumerated, are benzol sulphonamide,acetanilide, methyl acetanilide, ethyl acetanilide, acetamide, p-toluenemonocyclo hexyi sulphonamide.

Exudation frequently results also from the use of certain substancesincorporated as lubricants, e. g. ethyl p'almitate, aluminum palmitate,zinc stearate, stearic acid, carnauba wax, japan wax,

Lorol, a mixture of saturated fatty alcohols derived from thehydrogenation of cocoanut oil acids, -in which lauryl alcoholpredominates,

Lorol phthalate, the phthalic acid esters of this mixture, C18 alcohol,a mixture of saturated fatty alcohol isomers, chieflyof straightchaintype and chiefly with 18 carbon atoms in the chain.

Camphor, which is well known as the standard plasticizer for cellulosenitrate, has been disclosed as a plasticizer for cellulose acetate, buthas had practically no commercial use as such, because it is at best apoor solvent for cellulose acetate, tending to yield articles which areweak and brit- Tributyl phosphate has fire-- tie, and because further,perhaps of poor com-- patibility, it was tended to evaporate rapidlyfrom the finished product.

The present invention rests primarily upon the surprising discovery notonly that camphor will check the tendency to exudation on the part ofother plasticizers and of lubricants, from cellulose acetate compounds,but also that its presence in the compound, both per se and through itseffect of permitting the use of larger proportions of certain otherplasticizers, serves as a means of increasing flowab ility andmoldability without adverse effects upon toughness, stillness andsoftening temperature. When compounded to provide a product of a givenstiffness, the mixtures of the present invention are superior to thoseheretofore known in adaptability to molding processes, particularly themore exacting process of injection molding, and in toughness as measuredby the impact test (A. S. T. M. test D256-34T). Also they yield moldedarticles of superior gloss.

The invention resides further in the discovery of the ranges ofproportion of camphor and of other types of plasticizers which may beused to achieve these desirable results.

when plasticizers of the toughening exuding type are used without otherplasticizer, the resulting compound may have a satisfactory toughness,but it is subject to exudation, particularly in the presence oflubricants, and has certain deficiencies in molding characteristicswhich are particularly evident when the molding is done by injection, inthat, the material does not flow smoothly and does not come out of themold with a high gloss. Examination of the molded article gives evidenceof a non-homogeneity of structure resulting evidently from a prematurehardening of the material by cooling before the completion of thefilling of the mold. When it is attempted to overcome the defects ofmolding by increasing the content of plasticizer, the result is toemphasize the exudation, and also to impair the rigidity of the materialand lower its softening temperature, both to an undesirable degree.

When a proper proportion of the toughening exuding plasticizer in suchcomposition is replaced by camphor, to form compositions such 'as arehereinafter referred to as of type A, the

exudation of the toughening plasticizer is suppressed, and it thusbecomes feasible to use such plasticizers in substantial proportions.The smoothness of flow of the resulting compound in injection molding iscompletely satisfactory,

and the molded article as taken from, the mold is homogeneous and ofhigh gloss. Furthermore, in spite of this greater facility of molding,such a compound yields'a molded article which, for a given totalplasticizer content, is superior in rigidity to those of compositionscontaining no plasticizer other than one or more of the tougheningexuding group. 1

If triphenyl phosphate, or one of the other fireretarding plasticizersherein named, is introduced into a composition of type A, replacing acorresponding proportion of plasticizer in such a way that the relativeproportions of camphor, fire-retarding plasticizer and tougheningexuding plasticizer are within the range herein set forth as part of thepresent invention, the resulting material, designated herein as of typeB, has the advantageous properties already mentioned as characteristicof compounds of type A and in addi tion is of comparatively low burningrate. This is in marked distinction to the compositions which resultfrom the use of combinations of toughening exuding plasticizers andfire-retardingplasticizers of the group mentioned, in the absence ofcam- ,phor; such compositions do not have, for a given rigidity ofarticle, the outstandingly desirable molding properties which are ofparticular value and importance in injection molding, nor are they,

in general, free from exudation; except for their lower burning ratesthey are substantially the equivalents of compositions in which the onlyplasticizer used is one of those designated as toughening and exuding.

A further variation in the formulation in accordance-with the inventionresults in what is herein to'be referred to as type C, in which a type Chave, for a given total plasticizer content,

even better molding characteristics,particularly for injection molding,than those of compositions of type B, but it is recognized that thisadvantage is gained at the sacrifice of some degree of stability towardlight 'and heat, since the sulphonamide' plasticizer is likely tointroduce some degree of sensitivity to these influences. A practicallimit upon the proportion of aryl sulphonamide plasticizer is set bythis.factor and by the tendency I of these plasticizers to reduce thetoughness of the molded article. It has been found that in compositionsmade in accordance with this invention the totaL plasticizer content isdesirably between about 20 and 60 parts per 100 parts of'celluloseacetate. Compositions over thisentire range are useful in compressionmolding, while compositions containing from about 35 to 60 parts ofplasticizer are particularly desirable for use in injection molding.

Of the total plasticizercontent, the content of camphor should rangefrom 8 to 38 per cent, and

the preferred percentage is from. 13 to 17.

The remainder of the plasticizer content, 1. e.,

from 92-to62 percentof the plasticizer content,

may be constituted of one of the toughening exuding plasticizersalready-mentioned, or of a mixture of such a plasticizer with triphenylphos ticizers already mentioned, or of a mixture with such plasticizerand, in addition, one of the sub phate or one'of the otherfire-retarding ,plasphonamide plasticizers. These combinations will bedefined under the respective designations .of

types A, B and C.

Type A- -This contains- Tom plasticizer 26m 60 Total plasticizer 20 to60 and its plasticizer content is made up of Percent Camphor I 8 to 38;preferred 13 to 17 Fire-retarding plasticizer. 23 to 31; preferred 24 to28 .Aryl sulphonamide I plasticizer 2 to 6; preferred 3 to 5 Tougheningexuding A plasticizer 25 to 67; preferred 50 to 60 In general-the largerproportions of camphor,"

within the-stated range, will be desirable with cellulose acetates -oflow acetic numbers, and the smaller proportions with those of highacetic numbers. a

- The. benefits. resulting, from the presence of camphor in'compositions of typesB and C extend also in large degreeto modificationsof such compositions in which a non-exudingtoughening plasticizer suchas dimethyl phthalate is substit'uted for part or all .of the exudingtoughening plasticizer. I

It will be understood tlgt there may be present *in these compositions,in addition to the cellulose acetate and plasticizers, the proportionsof which form parts of the present invention; other ingredients also, inminor proportions asnormally met with in molding compounds, heretoforeknown, and including'dyestufis and pigments in quantities required forcoloration, residual volatile when the compound is to bemnldedbyinjection. The following examples are given to illustrate theinvention. -In these examples parts are given by weight, with additionalfigures in'parenthe- 'ses showing the percentage ratios of the contentsof individual plasticizers to the total content of plasticizers in therespective compositions.

(Total plasticizer 50) Examzlle 1 1 Parts Cellulose acetate 100 C:a.mphor i (15'%) 8 Dimethoxyethyl -phthalate .L- 46 (Total plasticizer"-54) Example 2 1 Y 4 Parts Celluiose acetate ;;r; Gamphor 18.8%) 9 Methylphthalyl ethyl glycollate (81.2%) 39 (Total plasticizer 48) I EmampZe3-'Parts Cellulose acetate 100 Camphorir. (1'6%) 8 Dimethoxyethylphthalate- (44% l T 22 Diethyl'phthalate; (40%)-; 20

Example 4 Example 15 v Parts p t Cellulose acetate 100 Cellulose acetateo Camphor Camphor (3o%) 15 5 Dimethoxyethyl phthalate (70.6%) 36Triphenyl phosphate (30%) 15 5 (Totalplasticlzer Diethyl phthalate (4o%)7 Example 5 (Total plastlcizer 50) Parts l0 Cellulose acetate 100Example 16 Camphor 2a%) 15 4 Parts Diethyl phthalate (72%) 39 \110 B 100(Total plasticizer 52) Camphor (8%) 4 Exam le 6 A T1 'iphenyl phosphate"(24%)-- 12 15 Parts D1methoxyethyl phthalate (oa% 35 15 Celluloseacetate 100 (Total ""'f 51) Camphor (8% 4 Dimethoxyethyl phthalate"(92%)" 4s, v Example 17 Parts 20 "T Example .7 Camphor (a%) 1.6

Part? Triphenyl phosphate 5 Cellulose tat 100 Dlethyl phthalate "(67%)"13.4 C mp 2 (Total plastlcizer 2o) 25 Dimethovyethyl phthalate "(92%) 2325 (Total plasticizer 25) Example 18 Example 8 p 7 Parts Parts Celluloseacetate 100 Cellulose acetate"; 100 Camphol 5 Camphor (s.3%) 5 T bu ylphosphate (23.4%)- 14 3o Diethyl phthalate (91.7%) 55 xye hyl phthalate(68.3%)-- 41 (Total plasticizer 60) (Total plastlcizel 6 Example 9Example 19 Cellulo'e acet to 35 Parts 35 camplfor a 5555" 7 Celluloseacetate 10o o Diethyl phthalate (65%) 13 i (Total plasticizer 2o)Tpphenyl PhOsphate 6 Dlethyl phthalate.- .(58.2%) 12.8 40 Example 10 A(Totalplasticizer 22) 40 Parts Cellulose acetate 100 Example 0 Camphor(38% 22 Parts D1methoxyethyl phthalate (62%) 36 Cellulose acetate 100 ol pl t r Camphor "(36%)" 9 45 Example 11 I Tricresyl phosphate "(24%)--6 Parts Diethyl phthalate (20%) 5 Cellulose acetate 100 Dimethylphthalate (20%) 5, Camphor "(15%)" 6 (Total plasticizer I 25) Trlethylcitrate (a5% 34 (Total plasticizer 40) Example 21 Parts Example 12 lParts gellulgse acetate 3 7 g 7 12(1) amp or a gg g gg ;-g Triphenylphosphate 25%) 14 55 m h Dimethoxyethyl phthalate (3'7.5%) 21 p nyl phsphat -3%) (Total 188mm 56) Dimethyl phthalate -(5s.2%) 32 P 60 T t l past mze Example 22 v Example 13 t Parts Parts Cellulose acetate 100Cellulose acetate Caniphorj. (14.5%) 6.3 Camphor 9 Trlphenyl phosphate(2'z.3%) 11.7 Triphenyl P P 12 Dimethyl phtha'lat (58.2%) 25 a 65Trlethyl citrate (20%) 10 (Total plastidizer 43)v Dimethoxyethylphthalate; "(38%)..- 19 l (Total plasticizer "50) Example 23 v p Example14 2 Parts g a t 1 Parts Celluloes acetate e- 100 70 Cellulose acetate 1100 Camphor- (20%) 8 Camphon -(28.8%) 15 Triphenyl phosphate, (30%).; 12"Iripheny1phosphate e (28.8%) 15 Dlmethoxyethyl phthalate (3'7.5%) 15Dlmethoxyethyl phthalate "(42.4%)" 22 Trlbutyl phosphate (12.5%) 5(Totalplasticizer -1 52) a 40) 75 (Total plasticlzer assumed, togetherwith a residual volatile solvent if such is characteristically theresult of a selected process of manufacture.

The present invention provides cellulose acetatecompositionscharacterized by a unique com-: bination of rigidity andtoughness together with an ease of molding not heretofore associatedwith compositions of such physical properties. Theirv use in place ofcompositions heretofore known for the manufacture of molded articles bycompression or by injection enable important savings to be made becauseof the ease with which they may be molded. They do not require to beheated to a high temperature nor for a long time, and are accordinglynot subject to the discoloring effect of such treatment. They do notrequire high pressure, and are accordingly readily molded in equipmentof ordinary construction. They may be molded on short cycles, and overrather wide ranges of molding temperature in comparison with the narrowcritical ranges of molding temperature which characterize many of thecellulose acetate molding compounds heretofore known. The compounds ofthe invention come with an unusually high gloss from a polished mold.

1. A plastic composition comprising 100 parts of cellulose acetate and20-60 parts of a'mixed plasticizer comprising 8-38% camphor and atleast25% of a toughening exuding plasticizer.

2. A plastic composition comprising 100 parts of cellulose acetate and20-60 parts of a mixed plasticizer consisting of 23-38% camphor and92-62% of a toughening exuding plasticizer.

' 3. A plastic composition'comprising 100 parts of cellulose acetate and20-60 parts of a mixed plasticizer consisting of 8-38% camphor and92-62% of a toughening exuding plasticizer from :the group consisting ofdiethyl phthalate, di-

methoxy ethyl phthalate, triethyl citrate, diethylene glycoldi-isobutyrate, diethylene glycol dipropionate, dimethyl hexahydrophthalate, diethyl adipate, methyl phthalyl ethyl glycollate, and ethylphthalyl ethyl glycollate.

4. A plastic composition comprising 100 parts of cellulose acetate and20-60 parts ofa mixed' plasticizer consisting of 8-38% camphor, 23-31%of a fire retarding plasticizer, and 31-69% of a toughening exudingplasticizer.

5. A'plastic composition comprising of cellulose acetate and 20-60 partsof a mixed plasticizer consisting of 8-38% camphor, 23-31% of a fireretarding plasticizer from the group consisting of triphenyl andtributyl phosphates, and 31-69% of a toughening exuding plasticizer fromthe group consisting of diethyl phthalate, dimethoxy ethyl phthalate,triethyl citrate, diethylene glycol di-isobutyrate, diethylene glycoldipropionate, dimethyl hexahydro phthalate, diethyl adipate, methylphthalyl ethyl glycollate, and ethyl phthalyl ethyl glycollate.

6. A plastic composition comprising 100 parts of cellulose acetate and20-60 parts of a mixed plasticizer consisting of 8-38% camphor, 23-31%of a me retarding plasticizer, 2-6% of an aryl sulphonamide plasticizer,and 25-67% of a toughening exuding plasticizer.

7. A plastic composition comprising 100 parts of cellulose acetate and20-60 parts of a mixed plasticizer consisting of 8-38% camphor, 23-31%of a fire retarding plasticizer from the group consisting of triphenyland tributyl phosphates, 2-6% of an .aryl sulphonamide plasticizer fromthe group consisting of toluol and toluol ethyl sulphonamides, and25-67% of a toughening exuding plasticizer from the group consisting ofdiethyl phthalate, dimethoxy ethyl phthalate, triethyl citrate,diethylene glycol di-isobutyrate, diethylene glycol dipropionate,dimethyl hexahydro phthalate, diethyl adipate, methyl phthalyl ethylglycollate, and ethyl phthalyl ethyl glycollate.

8. A molding composition adapted to be injection molded and comprising100 parts of cellulose acetate and 35-60 parts of a mixed plasticizerconsistingof 13-17% camphor and 87-83% of a toughening exudingplasticizer.

9. A molding composition adapted-to be injection molded and comprising100 parts of cellulose acetate and 35-60 parts of a mixed plasticizerconsisting of 13-17% camphor, 2428% of a fire retarding plasticizer, and55-65% of a.toughening exuding plasticizer.

l0. A molding composition adaptedto be injection molded and comprising100 parts of cellulose 5 acetate and 35-60 parts of a mixedplasticizerconsisting of 13-17% camphor,.24-28% of afire retarding plasticizer,3-5% of an aryl sulphona mide plasticizer, and 50-60% of a tougheningexuding plasticizer.

- MAURICE MACHT.

DAVID A. FLETCHER.

100 parts

